Electrical service disconnect having tamper detection

ABSTRACT

A tamper detection arrangement in a meter having a service disconnect switch employs a voltage sense circuit that requires only a single connection to digital processing circuitry for the feeder lines of typical residential service. In one embodiment, the voltage sense circuit includes an isolation device that electrically isolates the processing device from the line voltages. The voltage sense circuit senses a voltage on the feeder lines and is operable to generate a voltage detection signal having a characteristic representative of whether line voltage from the electrical power lines is present on the feeder lines. A processing circuit is operably connected to the voltage sense circuit to receive the voltage detection signal and to selectively generate a tamper flag based on whether the characteristic of the voltage detection signal indicates the presence of voltage on the first and second feeder lines when the service disconnect switch has disconnected the electrical power lines from the first and second feeder lines.

[0001] This application claims the benefit of U.S. Provisional PatentApplication Serial No. 60/272,023, filed Feb. 28, 2001, and which isincorporated by reference herein.

FIELD OF THE INVENTION

[0002] The present invention relates generally to electricity meters,and more particularly to electricity meters that are used in conjunctionwith load disconnect devices.

BACKGROUND OF THE INVENTION

[0003] Electrical service providers such as electrical utilities employelectricity meters to monitor energy consumption by customers (or otherentities). Electricity meters track the amount of energy consumed a load(e.g. the customer), typically measured in kilowatt-hours (“kwh”), ateach customer's facility. The service provider uses the consumptioninformation primarily for billing, but also for resource allocationplanning and other purposes.

[0004] Electrical power is transmitted and delivered to load in manyforms. For example, electrical power may be delivered as polyphasewye-connected or delta-connected power or as single phase power. Suchvarious forms are known as service types. Different standard electricitymeter types, known as meter forms, are used to measure the powerconsumption for the various service types. The commonly used meter formsin the United States include those designated as 2S, 3S, 5S, 45S, 6S,36S, 9S, 16S, 12S and 25S meter forms, which are well known in the art.

[0005] Electrical service providers have historically billed forelectrical service in arrears, using information stored within theelectricity meter to determine the amount of each invoice. In a typicaloperation, the electricity meter stores a value representative of theamount of energy consumed in a mechanical or electronic accumulationregister. From time to time, the electrical service provider obtains thevalue of the register and bills the customer accordingly. For example, ameter reader employed by the service provider may, each month,physically read the register value off a meter display. The serviceprovider then employs the obtained register value to determine theamount of electricity consumed over the month and bills the customer forthe determined amount.

[0006] A problem with the above-described operation of electricalservice providers arises from the fact that some customers arefrequently delinquent in or, in default of, payments for electricityconsumption. Because electrical service is billed in arrears, delinquentpayments can result in significant losses for the service provider.

[0007] In addition, interrupting the delivery of electrical power hashistorically been an expensive and significant event. Typically, atechnician must be dispatched to the customer's residence, or in thevicinity thereof, to physically disconnect the power. Accordingly, whilethe electrical service provider might physically disconnect the power tothe customer's facility for several months of complete payment default,physical disconnection is not practical in circumstances in whichcustomers are merely delinquent, or that can only pay portions of theirbills. In particular, the cost an effort of sending a technician out todisconnect electrical service is wasted if the customer pays a day ortwo later, thereby requiring another service call to restore service.

[0008] One method of controlling losses associated with delinquentcustomers is to require prepayment for services. In prepaymentarrangements, customers use prepaid debit cards or credit cards to“purchase” energy in advance. When the purchased energy has beenconsumed, the electrical service is disconnected. Thus, the serviceprovider is not exposed to extended periods of electrical service forwhich no payment may be provided. Another method of handling delinquentcustomers is to intermittently interrupt power to delinquent customersuntil the past due payments are made. Intermittent interruptions tend toreduce the amount of energy consumed by the delinquent payor, thusadvantageously reducing utility provider losses while also reducingbills to the delinquent payor.

[0009] Each of the above methods, however, typically requires theability to disconnect and/or reconnect the customer's power without atechnician service call to the customer's location. For example, in aprepayment scenario, the service provider must have a method ofdisconnecting power once the prepaid amount of energy has been consumed.Similarly, the intermittent interruption technique requires frequentconnection and disconnection of the electrical service.

[0010] One technique for automated or remote service disconnection is toemploy a service disconnect switch device within an electricity meter.The service disconnect switch is a relay or other device thatcontrollably disconnects and re-connects the utility power lines to thecustomer's feeder lines, thereby controllably interrupting power to thecustomer's facility. In some cases, the service disconnect switch istripped by a remote device that communicates with the electricity metercircuitry through a modem, radio or the like. Alternatively, such as inthe case of prepayment, the meter itself may be programmed to disconnectand reconnect electrical service under certain circumstances. In somesituations, the meter may disconnect and restore electrical servicethrough a combination of local programming and remote commands.

[0011] Thus, the inclusion of a service disconnect switch within a meterfacilitates various methods and techniques for providing electricalservice to parties that have poor payment records. Such methods andtechniques advantageously do not require a permanent disconnection by afield technician. The conveniences provided by a service disconnectswitch also extends beyond use in connection with delinquent payors. Forexample, electrical energy rationing may be implemented using techniquesenabled by the service disconnect switch.

[0012] Nevertheless, various issues that arise from the use of a servicedisconnect switch have not been adequately addressed in the prior art.For example, many of the above described service interruption techniquestypically require automated reconnection to be truly viable. In otherwords, if a technician must be dispatched every time power is to bereconnected to a customer after a service interruption, the convenienceand cost advantages of the automated disconnection are significantlyreduced.

[0013] Automatic reconnection of a customer's facility to electricalservice can raise potential dangers. For example, consider a situationin which the customer is operating a clothes iron or electric stove whenelectrical service is disconnected. If the customer does not remember toturn such a device off during the electrical service interruption, thenthe device will automatically resume operating again (at hightemperatures) when power is restored. The automatic restoration of ironor stove operation can create a fire hazard, particularly if thecustomer has since become otherwise occupied or has left the premises.Accordingly, restoring power through an automatically operated servicedisconnection switch raises some safety issues, as well as other issues.

[0014] In addition to safety issues, a drawback of service disconnectswitches is that they may be defeated through tampering either within orexternal to the meter. Such tampering typically involves placing abypass around the service disconnect switch. The bypass provides a paththrough which the customer may receive electrical power even though theservice disconnect switch has been opened.

[0015] One prior art device disclosed in U.S. Pat. No. 5,940,009 detectssuch tampering by detecting a voltage signal on the load-side connectionof a disconnect switch. In particular, this prior art device connectsthe load-side customer feeder lines to a processor through a voltagedivider. The processor then interprets the waveforms of from multiplefeeder lines to determine whether power is still being provided to theload even when a service disconnect switch has disconnected the serviceto the customer's load. The drawback of the device disclosed in U.S.Pat. No. 5,940,009 is that it requires multiple inputs to amicroprocessor to monitor multiple feeder lines, and further exposes themicroprocessor directly to the power line signals, albeit through avoltage divider.

[0016] Other issues with service disconnect devices within metersinclude whether and how a disconnect switch could be implemented in amodular meter. Modular meters are those that include separablecomponents. One removable component includes much of the meterelectronic and processing circuitry while the other component containshigh voltage sensor circuitry that interconnects with the power lines.Modular meters allow for easy enhancement of meter features andoperations because replacement of the removable component that includesthe meter electronic and processing circuitry typically suffices forsuch enhancements. Thus, to obtain improved functionality, only aportion of the meter must be replaced. Service disconnect switches donot readily lend themselves to modular meters because service disconnectswitches require both electronic and high power components, which aretypically separated into different modules of the modular meter.

[0017] There is a need, therefore, for an electricity meter that employsservice disconnect switch and that avoids one or more of the abovedescribed drawbacks. In particular, a need exists for an electricitymeter that includes a service disconnect switch having increased safetyenhancements associated with reconnecting a customer's electricalservice after an interruption. A need exists for an electricity meterthat obtains the benefits of both modularity in a meter and the use ofan automatically operated service disconnect switch within a meter.

SUMMARY OF THE INVENTION

[0018] The present invention fulfills the above needs, as well asothers, by providing a tamper detection arrangement in a meter having aservice disconnect switch that employs a voltage sense circuit thatrequires only a single connection to digital processing circuitry forthe two lines of typical residential service. In a preferred embodiment,the voltage sense circuit includes an isolation device that electricallyisolates the processing device from the line voltages.

[0019] In one embodiment of the invention, an apparatus for determiningtampering in an electricity meter arrangement is provided that comprisesa service disconnect switch operable to controllably disconnectelectrical power lines from a load including at least first and secondfeeder lines. The arrangement further includes a voltage sense circuitcoupled to sense voltage on the first and second feeder lines, in whichthe voltage sense circuit is operable to generate a voltage detectionsignal based on a first voltage on the first feeder line and a secondvoltage on the second feeder line. In one feature of the invention, thevoltage detection signal has a characteristic representative of whetherline voltage from the electrical power lines is present on the first andsecond feeder lines.

[0020] The arrangement further includes a processing circuit that isoperably connected to the voltage sense circuit to receive the voltagedetection signal. In accordance with the invention, the processingcircuit is operable to selectively generate a tamper flag based onwhether the characteristic of the voltage detection signal indicates thepresence of voltage on the first and second feeder lines when theservice disconnect switch has disconnected the electrical power linesfrom the first and second feeder lines.

[0021] In a further embodiment of the invention, an apparatus fordetermining tampering in an electricity meter arrangement comprises ahousing containing a metering circuit and a service disconnect switchdisposed within the housing. The service disconnect switch is operableto controllably disconnect electrical power lines from a load, the loadincluding at least first and second feeder lines. In one aspect of thisembodiment, a voltage sense circuit is coupled to sense voltage on atleast one feeder line, the voltage sense circuit including an isolationmechanism interposed between the at least one feeder line and an output.The voltage sense circuit is operable to generate a voltage detectionsignal having a characteristic representative of whether line voltagefrom the electrical power lines is present on the at least one feederline, and is further operable to provide the voltage detection signal tothe output. The apparatus can further include a processing circuitoperably connected to the output to receive the voltage detection signaland to selectively generate a tamper flag based on whether thecharacteristic of the voltage detection signal indicates the presence ofvoltage on the at least one feeder line when the service disconnectswitch has disconnected the electrical power lines from the first andsecond feeder lines.

[0022] A further embodiment of the invention contemplates a methodcomprising the step of disconnecting, using a service disconnect switch,at least one feeder line of a load from at least one electrical powerline, the service disconnect switch disposed within an electricity meterhousing. Another step of the method includes employing a voltage sensecircuit operably connected to the at least one power line to generate avoltage detection signal having a characteristic representative ofwhether line voltage from the electrical power lines is present on theat least one feeder line. The voltage detection signal is provided to anoutput that is electrically isolated from the at least one feeder line.In a further step, a processing circuit can be employed to receive thevoltage detection signal and generate a tamper flag if thecharacteristic of the voltage detection signal indicates the presence ofline voltage on the at least one feeder line.

[0023] In another feature, the voltage sense circuit can be employed togenerate the voltage detection signal such that the voltage detectionsignal has a first magnitude when line voltage is present on the atleast one feeder lines and the voltage detection signal has a secondmagnitude when line voltage is absent from the at least one feeder line.In still another feature, the voltage sense circuit can be employed togenerate the voltage detection signal such that the first magnitude andthe second magnitude are discrete digital voltage levels.

[0024] The above described features and advantages, as well as others,will become more readily apparent to those of ordinary skill in the artby reference to the following detailed description and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 shows a block diagram of an exemplary meter having aservice disconnect circuit arrangement in accordance with aspects of thepresent invention;

[0026]FIG. 2 shows an exploded perspective view of an exemplaryembodiment of a modular electricity meter that may incorporate a servicedisconnect arrangement in accordance with aspects of the presentinvention;

[0027]FIG. 3 shows a perspective view of the modular electricity meterof FIG. 2 implemented in an exemplary meter mounting device;

[0028]FIG. 4 shows a perspective view of a service disconnect switchmodule for use in the modular electricity meter of FIG. 2;

[0029]FIG. 5 shows a perspective view of an external interface assemblyfor use in the modular electricity meter of FIG. 2;

[0030]FIG. 6 shows a schematic diagram of the sensor module of themodular electricity meter of FIG. 2;

[0031]FIG. 7 shows a schematic diagram of the driver circuit of thesensor module of FIG. 6;

[0032]FIG. 8 shows a schematic diagram of the measurement module of themodular electricity meter of FIG. 2.

DETAILED DESCRIPTION

[0033] Referring now to the drawings, and more particularly to FIG. 1, adiagram of an electrical utility meter 100 constructed according toaspects of the present invention is shown. In FIG. 1, the meter 100 isoperably coupled to utility power lines 102. The utility power lines 102are connected to a source of electricity, such as a power transmissionand distribution system, not shown. A load 104 (typically a consumer ofelectrical power) is connected to the power lines 102 through feederlines 106. The meter 100 is operably coupled to the feeder lines 106 todetect the amount of electricity delivered to the load. The meter 100 isoperable to, among other things, generate metering informationrepresentative of a quantity of electrical energy delivered to the load104.

[0034] A housing assembly 112 is disposed over the meter 100 and encasesvarious components thereof. Voltage sensors 114 and current sensors 116are secured within the housing assembly 112, and are operable to receivevoltage and current signals representative of voltage and currentprovided to the load 104 and generate measurement signals therefrom. Inparticular, the measurement signals generated by the voltage sensors 114and current sensors 116 are analog signals each having a waveformrepresentative of the voltage and current provided to the load 104. Forpurposes of example and explanation, FIG. 1 illustrates two voltagesensors 114 and current sensors 116 for generating measurement signalsfor two-phase electrical service, or for two sides of a 240-voltsingle-phase three-wire electrical service. However, it will beintuitive to those skilled in the art that the principles of the presentinvention may also be applied to three-phase power systems.

[0035] A processing circuit 118 is operable to receive the analogmeasurement signals from the voltage sensors 114 and the current sensors116 and generate energy consumption data therefrom. According to anexemplary embodiment, the processing circuit 118 includes analoginterface circuitry 118 a that receives and digitizes the measurementsignals, and digital processing circuitry 118 b that processes thedigitized measurement signals to thereby generate the energy consumptiondata. Such circuits are well known in the art. According to analternative embodiment, however, the processing circuit 118 generatesthe energy consumption data by operating directly upon the analogmeasurement signals. As is known in the art, the processing circuit 118may include one or more integrated circuits.

[0036] The meter 100 includes a service disconnect circuit 120 thatincludes one or more service disconnect switches 120 a and a logicalcontrol portion 120 b. It will be appreciated that the logical controlportion 120 b and the processing circuit 118 may suitably share some orall of the same components and/or circuitry. However, in otherembodiments including the one described below in connection with FIGS. 2through 8, the control portion of the service disconnect circuit and theprocessing circuit of the meter are completely distinct circuits. Itwill also be appreciated that the control portion 120 b and the servicedisconnect switch 120 a may be housed in a single structure. However, inthe embodiment of FIGS. 2 through 8, the control portion located on acircuit board that is distinct from the service disconnect switch.

[0037] Referring again to FIG. 1, one or more service disconnectswitches 120 a are operably coupled to the processing circuit 118 withinthe housing assembly 112, and selectively connect and disconnect thepower lines 102 to the load 104 under the control of the processingcircuit 118. In general, the service disconnect circuit 120 has aconnected state, a disconnected state, and an armed state. The states ofthe service disconnect circuit 120 are maintained within the controlportion 120 b. The control portion 120 b controls the service disconnectswitches 120 a in accordance with the state logic.

[0038] More specifically, in the connected state, the service disconnectswitch 120 a operably couples the power lines 102 to the load 104 so asto provide electrical power thereto. In the disconnected and armedstates, the service disconnect switch 120 a operably decouples the powerlines 102 from the load 104 so as to remove the supply of electricalpower therefrom. Indeed, the control circuitry of the service disconnectswitch may constitute a portion of the processing circuit 118 of themeter.

[0039] The service disconnect circuit 120 changes from the connectedstate to the disconnected state in response to a first signal receivedfrom the processing circuit 118, and changes from the disconnected stateto the armed state in response to a second signal within the processingcircuit 118. It should be noted that the signals that cause the statechanges may be provided on one or more physical line A communicationcircuit 122 is operably coupled to the processing circuit 118, and isalso operable to receive signals from a remote device 124. Thecommunication circuit 122 may, for example, receive signals from theremote device 124 via a tangible communication link (e.g., cable, wire,fiber, etc.), or via a wireless communication link. According to oneaspect of the invention, the communication circuit 122 is operable toreceive a disconnect signal from the remote device 124. In response tothe disconnect signal, the communication circuit 122 providesinformation representative of the disconnect signal to the processingcircuit 118. The processing circuit 118 in turn provides the firstsignal to the control portion 120 b of service disconnect circuit 120,Thereby causing the service disconnect circuit 120 to change from theconnected state to the disconnected state. In the disconnected state,the service disconnect switches 120 a disconnect the feeder lines 106from the power lines 102.

[0040] According to another aspect of the invention, the communicationcircuit 122 is operable to receive an arm signal from the remote device124. In response to the arm signal, the communication circuit 122provides information representative of the arm signal to the processingcircuit 118. The processing circuit 118 in turn provides the secondsignal to the service disconnect circuit 120, thereby causing theservice disconnect circuit 120 to change from the disconnected state tothe armed state. In the armed state, as discussed above, the switches120 a do not immediately reconnect the feeder line 106 to the powerlines 102.

[0041] As will be more fully discussed below, the service disconnectcircuit 120 changes from the armed state to the connected stateresponsive to actuation of an externally accessible actuator 130.

[0042] One or more electronic indicators 126 are operably coupled to thecontrol portion 120 a and provide visual signals regarding operation ofthe service disconnect circuit 120. Each indicator 126 may, for example,be embodied as an indicator lamp including a light emitting diode, or asa liquid crystal display segment. According to an exemplary embodiment,each indicator 126 is visible external to the housing assembly 112 andis operable to provide a visual signal representative of the currentstate of the service disconnect circuit 120. For example, the indicator126 may include a first indicator lamp that provides a visual signalindicative of one or more service disconnect switches 120 in the armedstate, and a second indicator lamp that provides a visual signalindicative of one or more service disconnect switches 120 in thedisconnected state. Alternatively, the indicator 126 may be embodied asa single element which provides a first visual signal indicative of oneor more service disconnect switches 120 in the armed state, and a secondvisual signal indicative of one or more service disconnect switches 120in the disconnected state. It will be appreciated that in alternativeembodiments, the indicators 126 may be connected to the processingcircuit 118 as opposed to the control portion 120 a of the servicedisconnect circuit 120.

[0043] A display 128 is operably coupled to the processing unit 118 andprovides a visual display of information, such as information regardingthe operation of the meter 100. For example, the display 128 may providea visual display regarding the power measurement operations of the meter100. The display 128 and the indicator 126 may be separate and distinctelements of the meter 100, as shown in FIG. 1, or may be combined into asingle display unit.

[0044] An actuator 130 is operably coupled to each service disconnectswitch 120. When actuated, the actuator 130 causes one or more servicedisconnect switches 120 to change from the armed state to the connectedstate. The actuator 130 is coupled to the control portion 120 b of theservice disconnect switch 120, or may be directly coupled to eachservice disconnect switch 120. The actuator 130 is preferably disposedon the housing assembly 112, and is accessible from an external portionof the housing assembly 112. The actuator 130 may, for example, beembodied as one or more pushbutton mechanisms or other elements that maybe actuated by a user.

[0045] A voltage sense circuit 132 is coupled to sense voltage on one ormore of the feeder lines 106. According to an exemplary embodiment, thevoltage sense circuit 132 generates a voltage detection signal based ona first voltage on one feeder line 106 and a second voltage on the otherfeeder line 106. The voltage detection signal has a characteristicrepresentative of whether line voltage from the power lines 102 ispresent on one or more of the feeder lines 106. For example, the voltagesense circuit 132 generates the voltage detection signal having a firstmagnitude when line voltage is present on one or more of the feederlines 106, and having a second magnitude when line voltage is notpresent on one or more of the feeder lines 106. The first and secondmagnitudes of the voltage detection signal may correspond to discretedigital signal levels.

[0046] The processing circuit 118 is operably coupled to the voltagesense circuit 132 to receive the voltage detection signal. Theprocessing circuit 118 selectively generates a tamper flag based onwhether the voltage detection signal indicates the presence of voltageon one or more of the feeder lines 106 when one or more servicedisconnect switches 120 has disconnected the power lines 102 from one ormore of the feeder lines 106.

[0047] The above-described meter 100 thus incorporates the advantages ofhaving the externally accessible actuator 130, namely, to allow forrestoration of power after a disconnection by the service disconnectswitch that requires customer-side participation. As discussed above,such a requirement enhances safety by effectively preventing therestoration of power by the service disconnect switch when no one ispresent at the customer's facility. The advantages of the externallyaccessible actuator are enhanced through the optional use of electronicindicators that signal to the customer that the disconnect switch isarmed and that power may be restored.

[0048] The above-described meter 100 also provides an improved tamperprotection system that requires fewer connections to the digitalprocessing circuitry and preferably isolates the digital processingcircuitry from the power lines. In particular, by generating a singlevoltage detection signal based on the measurement of multiple feederlines, fewer inputs in a digital processing device need to be dedicatedto the operation of that circuit. It will be appreciated that theadvantages provided by improved tamper system may be obtained in metersthat do not include the externally accessible actuator described above.Similarly, it will be appreciated that the advantages provided by theexternally accessible actuator may be obtained in meters that do notinclude the improved tamper system described above.

[0049] While the above-described features provide at least someadvantages in any electricity meter that includes a service disconnectswitch, further advantages may be obtained through the implementation ofsuch features in a modular electricity meter. FIGS. 2 through 8 show anexemplary embodiment of a modular electricity meter 10 that incorporatesseveral aspects of the present invention.

[0050] In particular, FIG. 2 shows an exploded view of a modular meter10. In general, the meter 10 includes a sensor module 12 and ameasurement module 14. The measurement module 14 is constructed suchthat it may be removably coupled to the sensor module 12. Themeasurement module 14 and the sensor module 12 cooperate to form a typeof revenue meter known in the revenue metering industry as asingle-phase meter form. The single-phase meter form is the typetypically employed for stand-alone single-family dwellings. It will benoted, however, that the present invention is not limited to singlephase metering applications, but may readily be incorporated intopolyphase meter forms including, for example the commonly known 1S, 12S,and 25S meter forms.

[0051] The sensor module 12 includes voltage and current sensors, whichaccording to the exemplary embodiment described herein, include firstand second current transformers 16 a and 16 b, a plurality of currentblades 22 a, 22 b, 24 a, 24 b (current blade 22 b shown in FIG. 4), andone or more neutral blades 20. The current blades 22 a, 22 b, 24 a, and24 b are secured to the housing of a service disconnect switch 25. As isknown in the art the service disconnect switch 25 may suitably be anelectrically controlled relay. FIG. 4 shows a perspective view of theservice disconnect switch 25 and the current blades 22 a, 22 b, 24 a and24 b in further detail. As shown in FIG. 4, the service disconnectswitch 25 includes a housing 60 which houses the actual switchingrelays, not shown. Extending from the housing are lead wires 62 andconnection terminals 64 that provide the control connections to therelays inside of the housing.

[0052] In the exemplary embodiment described herein, the servicedisconnect switch 25 includes a 200 amp latching relay, such as onecommercially available from BLP of the United Kingdom. The latchingrelay has the characteristic of changing state (closed to open or opento closed) upon receipt of a characteristic input signal, and thenretaining the state when the signal is removed, only changing state uponreceipt of a different characteristic signal. However, in otherembodiments, a normally open or normally closed relay may be employed,although at some loss of efficiency. The use of a 200-amp relaycorresponds to the typical 200 amp residential electrical service.Relays having other capacities may be used if desired to accommodateelectrical service rated at a different quantity of amps.

[0053] Further detail regarding the electrical connections between thecurrent blades 22 a, 22 b, 24 a, and 24 b is and the service disconnectswitch 25 is provided below in connection with FIG. 6, which shows aschematic diagram of sensor module 12.

[0054] The current blades 22 a, 22 b, 24 a and 24 b are configured to bereceived by jaws of a standard meter mounting device. FIG. 3 shows,among other things, an exemplary meter mounting device including jaws 22in which the current blades 22 a, 22 b, 24 a and 24 b are received.

[0055] The first and second current transformers 16 a and 16 b,respectively, are preferably toroidal transformers having asubstantially circular shape defined by a circular core. In the presentembodiment, the first current transformer 16 a has a turns ratio of N1and the second current transformer 16 b has a turns ratio of N2. Thecurrent blade 22 a passes through the interior of the toroid formed bythe first current transformer 16 a and the current blade 22 b passesthrough the interior of the toroid formed by the second currenttransformer 16 b. Accordingly, the current transformers 16 a and 16 bare in a current sensing relationship with the current blades 22 a and22 b, respectively.

[0056] Also enclosed within the housing 12 a of the sensor module 12 isa driver circuit board 23 and an interface assembly 27. The drivercircuit board 23 provides the structure on which is disposed the drivercircuit (illustrated in FIG. 7). The driver circuit board 23 includesfirst and second actuators 78 and 80, discussed in additional detailfurther below. The driver circuit board 23 further includes a ribbonconnector assembly 88. The ribbon connector assembly includes a firstconnector block 88 a secured to the driver circuit board 23, a ribbonconnector 88 b, and a second connector block 88 c for connection to themeasurement circuit of the measurement module 14. The interface assembly27 is a subassembly that includes a plurality of indicators 52, 54, apushbutton actuator 56, and corresponding lead wires 58.

[0057] More specifically, FIG. 5 shows the interface assembly 27 and anunderside view of the housing 12 a. Referring to FIG. 5, the housing 12a is shown without any of the elements mounted therein for purposes ofclarity of exposition of the connection of the interface assembly 27 tothe housing 12 a. In general, the housing 12 a is preferably a moldedplastic cylindrical shaped container for receiving the components of thesensor assembly 12 illustrated in FIG. 2. Referring again to FIG. 5, thehousing 12 a includes, on an inner side thereof, a molded seatingstructure 66 designed to receive the interface assembly 27 therein. Themolded seating structure 66 is integrally molded with the housing 12 aproximate the periphery of the housing 12 a adjacent apertures 68, 70and 72. The apertures 68, 70 and 72 provide openings from the interiorof the housing 12 a through which the indicators 52, 54 may be viewedand through which external access to the actuator 56 is provided.

[0058] In particular, when the interface assembly 27 is seated withinthe molded seating structure 66, the indicators 52, 54 extend partiallyinto or through the apertures 68, 70 respectively and the actuator 56extends partially through the aperture 72. Because the apertures 68, 70and 72 provide communication between the interior of the sensor housing12 a and the exterior, arrangements are provided to isolate the interiorof the sensor housing 12 a from significant exposure to externalcontaminants, moisture and the like. To this end, the interface assembly27 includes an elastomeric boot or seal 74 that extends over theactuator 56. The elastomeric seal 74 includes a base 74 a that is wedgedbetween a U-shaped switch bracket 76 and one or more sealing washers 79within the seating structure 66. The actuator 56 and the seal 74 extendat least partially through the aperture 72 to the exterior of thehousing 12 a. In this position, a person external to the meter 10 mayactuate the actuator 56 by depressing the elastomeric seal 74 andactuator 56. The seal 74 and the sealing washers 79 allow for externaloperation of the movable actuator 56 without exposing the interior ofthe housing, which includes high voltage and current components, tosignificant amounts of environmental moisture or contaminants.

[0059] To inhibit contamination or moisture ingress through theapertures 68 and 70, first and second sealing lenses 52 a and 54 a areprovided that extend over the indicators 52 and 54, respectively. Thelenses 52 a and 54 a provide the necessary sealing function while alsopermitting the light from the indicators 52 and 54 to radiatetherethrough.

[0060] The sensor module 12 further includes an electrically safeinterface 26. The electrically safe interface 26 comprises a firstinterconnecting means for connecting to the measurement module 14. Theelectrically safe interface 26 also includes means for preventingphysical contact of a human operator with potentially hazardouselectrical signals present on at least a portion of the voltage andcurrent sensors 15. Signal levels which are considered potentiallyhazardous are well known. Different levels of potential hazard alsoexist. For example, signals capable of generating shock currentsexceeding 70 milliamperes are possible burn hazards, while signalsgenerating shock currents on the order of 300 milliamperes mayconstitute life-threatening hazards. Furthermore, signals generatingshock currents as low as 0.5 to 5 milliamperes are known to cause aninvoluntary startle reaction.

[0061] In revenue meters, at least some of the sensor devices carry suchpotentially hazardous electrical signals. Specifically, any portion of ameter that is electrically connected to the voltage and current signalsfrom the power line constitutes a life-threatening hazard. Theelectricity meter 10 of the present invention isolates the voltage andcurrent sensors by placing them within the meter mounting device 13 andproviding the electrically safe interface 26. In the present embodiment,the current blades 22 a, 22 b, 24 a and 24 b are directly connected tothe facility power line and therefore must be isolated. Although otherportions of the sensors 15 may not be directly connected to the powerlines, the electrically safe interface 26 preferably prevents humancontact with all of the voltage and current sensors 15 as a safetymeasure.

[0062] In the present embodiment, the means for preventing physicalcontact includes a top plate 28, a plurality of sockets 30 a, 30 b, 30c, 30 d, 30 e, 30 f and 30 g, the actuators 78 and 80 and the connectorblock 88 a of the driver circuit board 23. Each of the sockets 30 athrough 30 g defines an opening in the top plate 28. Two other openingsin the top plate 28 include actuator openings 82 and 84 which receivethe actuators 78 and 80 from the driver circuit board 23. Yet anotheropening in the top plate 28 is a connector opening 86 through which theconnector block 88 a of the driver circuit board 23 extends. Other thanthe above-described openings, the top plate 28 preferably forms acomplete barrier or wall from the measurement module 14 to the voltageand current sensors 15.

[0063] At a minimum, the top plate 28 operates to prevent human contactwith the portions of the voltage and current sensors 15 that directlycontact the power lines of the facility, and in particular, the currentblades 22 a, 22 b, 24 a and 24 b.

[0064] In order to provide a complete barrier, the top plate 28cooperates with the enclosure base 16 and a cover of a cooperating metermounting device (See, e.g. FIG. 3) that enclose the voltage and currentsensors 15 from the side and bottom. In another alternative embodiment,the top plate 28 may be integrally coupled to such a cover.

[0065] Referring again to FIG. 2, the sockets 30 a through 30 g andtheir corresponding openings are preferably configured to prevent ahuman operator from physically contacting the electrically conductiveportions of the socket. In particular, the openings defined by thesockets 30 a through 30 g have sufficiently small proportions to preventcontact of a standard test finger with the electrically conductiveportions of the sockets 30 a through 30 g. A standard test finger is amechanical device used in the electrical industry to determine whetheran electrical connection socket is safe from accidental contact by ahuman finger. One standard test finger is described in Underwriter'sLaboratory, Inc., Standard for Safety of Information TechnologyEquipment Including Electrical Equipment Business UL-1950 (Feb. 26,1993).

[0066] In the present embodiment, the openings defined by the sockets 30a through 30 g preferably have a first dimension, for example, thelength, and a second dimension, for example, the width, wherein thefirst dimension has at least the same size as the second dimension, andthe second dimension is less than {fraction (1/8)} inch, therebypreventing substantial access of a human operator through the openings.

[0067] As will be discussed below, one of the advantages of the abovedescribed sensor module 12 arises from the inclusion of the actuators 78and 80 that are accessible on the electrically safe interface 26. Theelectrically safe interface 26 is generally inaccessible to customersand other parties because it is typically covered or closed off by themeasurement module 14 when the meter 10 is assembled and operational.Accordingly, the actuators 78 and 80 are accessible only to personsauthorized to remove the measurement module 14.

[0068] The actuators 78 and 80 in the present embodiment provide signalsthat can disconnect (open) and arm the service disconnect switch 25. Ina device without a separate “armed” state, the actuators 78 and 80 maybe coupled directly to the switch 25 to either open or close the switch25. In any event, the actuators 78 and 80 provide a convenient andintuitive means by which an authorized technician may manipulate theservice disconnect switch 25 without allowing customer access to suchmeans.

[0069] The measurement module 14 comprises a face cover 32, a printedcircuit board 34, and a gasket 36. The printed circuit board 34 includesa display 38, and a measurement circuit. FIG. 8, discussed furtherbelow, shows a schematic block diagram of a measurement circuit 42 thatmay readily be used as the measurement circuit on the printed circuitboard 34 of FIG. 2. The measurement circuit is operable to receivemeasurement signals and generate energy consumption data therefrom. Themeasurement circuit is operably connected to provide the energyconsumption data to the display 38.

[0070] The measurement module 14 further includes second interconnectingmeans operable to cooperate with first interconnecting means (on thesensor module 12) to connect the measurement circuit of the printedcircuit board 34 to the voltage and current sensors 15. For example, inthe present embodiment, the measurement module 14 includes a pluralityof plugs 40 a through 40 g that are received by the correspondingplurality of sockets 30 a through 30 g. The plurality of plugs 40 athrough 40 g, when assembled, are electrically connected to themeasurement circuit and physically connected to the printed circuitboard 34. The printed circuit board 34 further includes a block, notshown, configured to receive the connector block 88 c of the connectorassembly 88.

[0071]FIG. 3 shows an installation configuration that includes the meter10 and a meter box 13 comprising a housing 16 and a cover 18. Thehousing 16 is box-like in structure having an opening for receiving thecover 18 and a cabling opening 24 for receiving the power lines of theelectrical system being metered, not shown. It will be appreciated thatthe housing 16 need not be box-like in structure, and that any othersuitable shape may be used, as long as there is an opening for receivinga cooperating meter box cover and a cabling opening. The housing 16further includes an interior 20. Within the interior 20 are located aplurality of jaws 22 constructed of electrically conductive material.When installed into a facility, the plurality of jaws 22 areelectrically connected to the power lines of the electrical system ofthe facility.

[0072] The plurality of jaws 22 receive and provide electricalconnection to the current blades 22 a, 24 a, 22 b and 24 b (see FIG. 2)as well as the neutral blade or blades 20. The relationship of the jawsand the blades 22 a, 24 a, 22 b, and 24 b also define the alignment ofthe sensor module 12 within the housing 16. Once the blades 22 a, 24 a,22 b, and 24 b (see FIG. 2) are engaged with the plurality of jaws 22(FIG. 3), the sensor module 12 is installed within the interior 20 ofthe housing 16. The cover 18 is then installed onto the housing 16. Thecover 18 includes a meter opening 18 a having a perimeter defined by theperimeter of the sensor module 12. Preferably, the perimeter of themeter opening 118 a has substantially the same shape and is slightlysmaller than the perimeter of the sensor module 12 such that the sensormodule 12 cannot be removed when the cover 18 is engaged with thehousing 16.

[0073] Once the cover 18 is installed, the measurement module 14 in thepresent embodiment is placed in engagement with the sensor module 12through the meter opening 18 a of the meter box cover 18. Prior to suchengagement, the connector block 88 c of the ribbon connector assembly 88is coupled to the corresponding connector, not shown, on the measurementmodule 14. After connection of the connector block 88 c, the measurementmodule 14 is aligned over the sensor module 12 and then coupled thereto.When in engagement, the plugs 40 a through 40 g of the measurementmodule 14 are electrically connected to the sockets 30 a through 30 g,respectively, of the sensor module 12.

[0074] In particular, as discussed above, the top plate 28 includes aplurality of sockets 30 a, 30 b, 30 c, 30 e, 30 f and 30 g. Each socket30 x has an opening for receiving a corresponding plug 40 x that ispreferably slightly conical to allow for alignment adjustment of theplug 40×during assembly of the measurement module 14 onto the sensormodule 12. The socket 30 x , which may suitably include a spring loadedterminal, is electrically connected to one of the current blades 24 a or24 b for the purposes of obtaining a corresponding phase voltagemeasurement, as will be more fully discussed below.

[0075] Each plug 40 x is connected to the circuit board 34 and isconfigured to be inserted the socket 30 x. The socket 30 x physicallyengages the plug 40 x in such a manner as to provide an electricalconnection therebetween. To this end, the plug 40 x may suitably be anordinary conductive pin. Further detail regarding the sockets 30 x, theplugs 40 x, and an exemplary illustration of their structure andinterrelationship may be found in U.S. Pat. No. 5,933,004, which isincorporated herein by reference.

[0076] Once the measurement module 14, the cover 18, the sensor module12, and the housing 16 are all assembled as described above, the meter10 (i.e., the sensor module 12 and the measurement module 14) performsenergy consumption measurements on the electrical system of thefacility.

[0077] It is noted that the meter 10 preferably includes one or moredevices or arrangements that inhibit tampering. As discussed above inconnection with FIG. 1, one method of tampering involves bypassing themeter 10 and/or the service disconnect switch 25 in the sensor module12. Devices for inhibiting such tampering are discussed in furtherdetail below in connection with FIGS. 6, 7 and 8. However, anothermethod of tampering with a modular meter such as the meter 10 is toremove the measurement module 14 so that energy flowing through thesensor module 12 is not recorded in the measurement circuit.

[0078] In particular, it is noted that if the measurement module 14 isremoved from the sensor module 12, the facility to which the meter 10 isconnected will continue to receive electrical power service, but willnot be charged for such power usage. The facility will not be chargedfor such power usage because the billing information is generallyobtained from the energy consumption data in the measurement module 14,and the measurement module 14 does not generate any energy consumptiondata when the measurement module 14 is removed from the sensor module12. Accordingly, a potential method of meter tampering is to remove themeasurement module 14 from the sensor module 12 for a few hours a day,or for one or more days, and then replace the measurement module 14before utility service provider personnel comes to read the meter.

[0079] Exemplary arrangements for preventing such tampering in a modularmeter such as the meter 10 are disclosed in U.S. Pat. No. 6,275,168 andU.S. patent application Ser. No. 09/667,888, filed Sep. 22, 2000, bothof which are assigned to the assignee of the present invention and areincorporated herein by reference. In the alternative or in addition,electronic arrangements that detect and record removal of themeasurement module 14 may be employed, such as that described in U.S.patent application Ser. No. 09/345,696, filed Jun. 30, 1999, which isalso incorporated herein by reference. Such arrangements typicallygenerate a mechanical or electronic record indicating that themeasurement module 14 has been removed, so that tampering becomesevident to the utility.

[0080] The configuration of the meter box 13 in FIG. 3 is a standardmounting device known as a ringless-type mounting device. It will benoted that the meter 10 may readily be adapted for use in a ring-typemounting device as well. A ring-type mounting device differs from themeter box 13 in FIG. 3 in that the sensor module 12 would be installedafter the meter box cover 18 is assembled onto the housing 16. Anannular ring would then be used to secure the sensor module 12 to themeter box cover 18. To this end, the standard meter box cover for use ina ring type mounting device includes a feature annularly disposed aroundthe opening 18 a which cooperates with the annular ring to engage andsecure the sensor module 12 thereto.

[0081] It can thus be seen by reference to FIGS. 2 and 3, that theelectrically safe interface 26, when fitted to the meter mounting devicehousing 16 and the cover 18, provides a substantially solid barrierbetween a human operator or technician and the current and voltagesensing devices when the measurement module 14 is removed for repair orreplacement. The only openings in the interface are of insufficient sizeto receive a human finger. The openings 82, 84 and 86 are closed off by,respectively, the actuators 78, 80 and the connector block 88 a. Theopenings that correspond to the sockets 30 a through 30 g aresufficiently small enough, and the sockets are sufficiently recessedwithin the openings, to prevent an operator from coming into directcontact with dangerous high voltages. In addition, even if the connectorblock 88 a is removed, the operator or technician is only exposed to apin array (see pin array 221 of FIG. 7). In accordance with theexemplary embodiment described herein, the pin array contains onlynon-hazardous voltages, preferably isolated from the utility power lines(see pin array 221 of FIG. 7).

[0082] It will be appreciated that other interconnection means may beemployed in the sensor module 12 and measurement module 14 that willalso provide an electrically safe interface. For example, wireless meansmay be used as the interconnection means. Such wireless means couldprovide voltage and current measurement signals from the sensor module12 to the measurement module 14. For example, the measurement module 14could include sensitive electric and magnetic field sensors that obtainvoltage and current measurement information from electromagneticradiation from the current and voltage sensors 15. Likewise, opticalcommunication means may be used to provide measurement signalinformation from the sensor module 12 to the measurement module 14. Inany case, the electrically safe interface would typically include abarrier such as the top plate 28 that prevents physical access by ahuman operator to the dangerous portions of the voltage and currentsensors 15 when the measurement module 14 is removed.

[0083] To fully obtain the benefits of modularity, it is necessary toaddress calibration issues in the design of the meter assembly 10.Specifically, the sensor module 12 preferably has a calibration featurethat allows it to be used in connection with any suitable measurementmodule.

[0084] By contrast, in traditional meters where the sensor circuit andthe measurement electronics are housed together as a single unit, themeasurement circuit is often specifically calibrated for use with aparticular voltage and current sensors. The reason for the specificcalibration is that there can be significant error in signal response ofeach voltage and current sensors. In particular, the current sensingdevices, such as current transformers, often have a widely variablesignal response error. In other words, the signal response error of anytwo current sensing devices can vary to a significant degree. The signalresponse error of commonly available current transformers affects bothmagnitude and phase response.

[0085] The signal response error of such current transformers typicallyexceeds the amount of energy measurement error that can be tolerated inthe meter. In other words, while the current transformer signal responseerror may reach as much as 10%, the measurement error of the meter mustbe much less than 10%. Accordingly, compensation must be made for thevariance, or tolerance, of the current sensing devices to ensure thatthe ultimate energy measurement accuracy of the meter is withinacceptable tolerances. The compensation is typically carried out in theprior art by adjusting or calibrating the measurement circuit duringmanufacture to account for the signal response characteristics of thecurrent sensing devices that will be used in a particular meter unit. Inother words, each measurement circuit is custom-calibrated for eachmeter.

[0086] The meter assembly 10, however, should not require such extensiveunit-specific calibration. In other words, the sensor module 12 shouldbe able to receive any of a plurality of measurement meters 14 withoutextensive calibration operations. Accordingly, referring again to FIG.2, the sensor module 12 is pre-calibrated for modularity, such that thesensor module 12 may be coupled with any measurement module 14 withoutrequiring unit-specific calibration of that measurement module 14.

[0087] To this end, the sensor module 12, and specifically the voltageand current sensors 15 are pre-calibrated such that the voltage andcurrent sensors 15 have a signal response within a tolerance of apredefined signal response that is no greater than the tolerance of theenergy measurement accuracy of the meter assembly 10. The energymeasurement accuracy of the meter assembly 10 may be defined as theaccuracy of the measured energy consumption with respect to the actualenergy consumption of the facility. Thus, if the tolerance of the energymeasurement accuracy of the meter is required to be 0.5%, then thedifference between the measured energy consumption and the actual energyconsumption will not exceed 0.5%. In such a case, the tolerance of thesignal response of the voltage and current sensors will be no more than,and typically substantially better than, 0.5%. As a result, themeasurement module 14 may readily be replaced with another measurementmodule without requiring specific calibration of the replacementmeasurement module.

[0088] The pre-calibration of the voltage and current sensors 15 may beaccomplished using careful manufacturing processes. The primary sourceof variance in the signal response of the voltage and current sensors 15is the signal response of the current transformers 16 a and 16 b.Generally available current transformers are prone to variance in bothmagnitude and phase angle signal response. Accordingly, pre-calibrationinvolves using current transformers that are manufactured to performwithin the required tolerances. As an initial matter, the currenttransformers 16 a and 16 b are manufactured using a high permeabilitycore material, which reduces phase angle variance in the signalresponse. Moreover, the current transformers 16 a and 16 b aremanufactured such that the actual number of turns is closely controlled.Close manufacturing control over the number of turns in the currenttransformers 16 a and 16 b produces sufficient consistency in themagnitude signal response to allow for interchangeability.

[0089] Alternatively, if controlling the number of turns during initialmanufacturing is not desirable for cost reasons, then turns may be addedor removed after manufacturing to achieve the desired signal response.For example, it may be more cost effective to buy wide tolerancecommercially available current transformers and adjust the number ofturns than to have sufficiently narrow tolerance current transformersspecially manufactured.

[0090] Still another method of obtaining calibration would be to useinexpensive wide tolerance current sensing devices and then storecalibration information directly in the sensor module 12 that may becommunicated to each measurement module 14 as it is connected. Such anarrangement in a modular meter is described in U.S. Patent ApplicationSerial No. 60/325,030, filed Sep. 25, 2001, which is incorporated hereinby reference.

[0091] Referring now to the circuit block diagram in FIG. 6 of thesensor module 12 of FIG. 2, the sockets 30 a and 30 b provide aconnection to the first current transformer 16 a, the sockets 30 e and30 f provide a connection to the second current transformer 16 b, thesocket 30 c provides a connection to the current blade 24 a, the socket30 d provides a connection to the current blade 24 b, and the socket 30g provides a connection to one or more of the neutral blades 20.

[0092] The sensor module 12 further includes the service disconnectswitch 25. As shown herein, the service disconnect switch 25 includes afirst switching contact 25 a and a second switching contact 25 b. Theservice disconnect switch further includes control signal lines 25 c and25 d that are operably coupled to the driver circuit 210.

[0093] In an ordinary residential “single phase” meter, the currentblade 24 a connects to a first high side of a 240-volt incoming utilitypower line and the current blade 24 b connects to a second high side ofthe 240-volt incoming utility power line. The utility current blade 24 aconnects through the first switching contacts 25 a to a first feederline of the customer load via the current blade 22 a. Similarly, theutility current blade 24 b connects through the second switchingcontacts 25 b to a second feeder line of the customer load via thecurrent blade 22 b. The current transformer 16 a is disposed in acurrent sensing relationship with the current flowing to the firstfeeder line through the current blade 22 a. The current transformer 16 bis disposed in a current sensing relationship with the current flowingthrough the second feeder line through the current blade 22 b.

[0094] The driver circuit 210 is operably coupled to communicate to anexternal device, and namely, the measurement module 14, through theconnector ribbon assembly 88. The driver circuit 210 is furtherconnected to provide control signals the switching contacts via signallines 25 c and 25 d. The driver circuit 210 is operably connected tocontrollably energize the indicators 52 and 54, and to detect actuationof any of the actuators 56, 78 and 80.

[0095]FIG. 7 shows in further detail a schematic of the elements of thedriver circuit board 23 including primarily the driver circuit 210. Inaddition to the driver circuit 210, as discussed above in connectionwith FIG. 2, the driver circuit board 23 further includes the actuators78 and 80 and the connector block 88 a.

[0096] The driver circuit 210 includes a digital control circuit 212,timer/clock circuitry 213, a power supply circuit 214, a voltage sensecircuit 216, I/O interface circuitry 218, external interface drivecircuitry 220 and disconnect switch drive circuitry 222.

[0097] The power supply circuit 214 is preferably coupled to the currentblades 24 a and 24 b to obtain external power even when the servicedisconnect switch 25 is open (in the disconnected state or armed state).The power supply circuit includes a transformer 224, a diode bridgecircuit 223, and regulator circuit 225 configured as is well known inthe art to provide a DC power supply output voltage VCC derived from anAC input voltage.

[0098] The voltage sense circuit 216 is a circuit operably coupled tosense whether line voltage is present on the feeder lines of thecustomer load. To this end, the voltage sense circuit 216 includesinputs 226 and 228 electrically connected to the current blades 22 a and22 b (see FIG. 6) to obtain any voltages present in the feeder lines tothe customer load. The input 226 connects to the input 228 through aresistive network 230 and a bi-directional input 232 of an opticalisolation circuit 234. As a result, a voltage divider is formed at theinput 232 of the optical isolation circuit 234 by the resistive network230 and the inherent impedance of the bi-directional input 232.

[0099] It will be appreciated that the resistive network 230 maysuitably be one or many resistors, so long as the total resistance valueis selected to provide an appropriate amount of drop over thebi-directional input 232 at a relatively low current. Moreover, it willbe noted that an additional resistor may be coupled across thebidirectional input 232 if necessary to reduce the drop over thebi-directional input 232.

[0100] The optical receiver/output 236 of the optical isolation circuit234 is coupled between the power supply voltage VCC and an output EXT1of the connector block 88 a. A capacitor 238 is coupled between theoutput EXT1 and ground. Accordingly, when the input 232 of the opticalisolation is biased on, then the optical receiver/output 236 propagatesthe VCC supply voltage (logic high) to the output EXT1, also chargingthe capacitor 238. When the input 232 is not biased on, then the opticalreceiver/output 236 opens the connection between the VCC supply voltageand the output EXT1. The capacitor 238 discharges and then little or novoltage (logic low) propagates to the output EXT1. In general, theoutput EXT1 is provided to the processing circuitry in the measurementmodule 14 to aid in the detection of a form of tampering in which thesensor module 12 and/or the disconnect switch 25 is bypassed.

[0101] The timer/clock circuitry 213 comprises timer circuitry thatprovides clocking signals to the digital control circuit 212. Suchdevices are well known. The I/O interface circuitry 218 provides buffercircuitry that allows the digital control circuit 212 to receive inputfrom and provide output to various devices. For example, the I/Ointerface 218 allows for a bi-directional serial data communication lineto the processing circuitry of the measurement module 14 through theconnector block 88 a. The I/O interface 218 also operably provides thedigital control signal 212 with a signal representative of the status ofthe actuators 78 and 80. The external interface drive circuitry 220provides the drive circuitry necessary to cause the indicators 52, 54,which in the exemplary embodiment described herein are light emittingdiodes (“LEDs”), to illuminate in response to appropriate digital outputsignals generated by the digital control circuit 212. The externalinterface drive circuitry 220 further enables the digital controlcircuit 212 to obtain a digital signal representative of the status ofthe actuator 56.

[0102] The disconnect switch drive circuit 222 includes circuitry thatenables the digital control circuit 212 to cause the switch contacts 25a and 25 b to open and close. In particular, the digital control circuit212 includes a CLOSE output and an OPEN output. The CLOSE output iscoupled to the input/transmitter 250 of an optical isolation circuit 252and the OPEN output is coupled to the input/transmitter 254 of anoptical isolation circuit 256. The output/receivers 258, 260 of theoptical isolation circuits 252, 256 respectively, are coupled to firstand second AC power line voltages (i.e. the line voltages on currentblades 24 a and 24 b) in a manner configured to generate relatively highpower control signals at an output connector 262. For example, theoutput/receiver 258 allows AC power line current to flow temporarily tothe connector 262 and the output/receiver 260 allows AC power linecurrent to flow temporarily from the connector 262. The output connector262 is coupled to the control lines 25 c and 25 d of the disconnectswitch 25.

[0103] In general, the disconnect switch drive circuit 222 operates toprovide the AC power line control signal to the control lines 25 c and25 d that signal causes the switch contacts 25 a and 25 b to openresponsive to a logic high signal on the OPEN output of the digitalcontrol circuit 212. The disconnect drive circuit 22 further operates toprovide the AC power line control signal to the control lines 25 c and25 d that causes the switch contacts 25 a and 25 b to close responsiveto a logic high signal on the CLOSE output of the digital controlcircuit 212.

[0104] The digital control circuit 212 may suitably comprise a processoror one or more programmable logic devices operably to carry out basiclogical functions in the control of the service disconnect switch 25,and the indicators 52 and 54. The digital control circuit 212 and theservice disconnect switch 25 form a service disconnect circuit having adisconnected state, an armed state, and a connected state. The digitalcontrol circuit 212 generally controls the change of states of thecircuit and the outputs generated as a result of such changes in state.

[0105] In particular, the digital control circuit 212 is operable tochange from the connected state to the disconnected state, from thedisconnected state to the armed state, and from the armed state to theconnected state. In general, the digital control circuit 212 causes theswitch contacts 25 a and 25 b to be open when transitioning into thedisconnected state, thereby disconnecting the electrical service to theload. The digital control circuit 212 further causes the switch contacts25 a and 25 b to be closed, thereby restoring service to the load whentransitioning from the armed state to the connected state. In the armedstate, the digital control circuit 212 leaves the switch contacts 25 aand 25 b open.

[0106] The digital control circuit 212 changes state in response tovariety of inputs. In general, the digital control circuit 212 changesfrom the connected state to the disconnected state in response to serialcommunication signals received from the processing circuit of themeasurement module 14 (i.e. the processor or controller 48 of FIG. 8)through the connector block 88 a. The digital control circuit 212 alsochanges from the connected state to the disconnected state in responseto actuation of the actuator 78, which operates as a disconnect switch.In response to the change from the connected state to the disconnectedstate, the digital control circuit 212 generates a logic high signal onits OPEN output, thereby causing the switch contacts 25 a and 25 b toopen. In addition, the digital control circuit 212 generates a logichigh signal on the output that causes the indicator 52 to becomeilluminated. Finally, the digital control circuit 212 generates a signalidentifying the change in state to the processor 48 of the measurementmodule 14 via the connector block 88 a.

[0107] The digital control circuit 212 changes from the disconnectedstate to the armed state in response to serial communication signalsreceived from the processor 48 of the measurement module 14 through theconnector block 88 a. The digital control circuit 212 also changes fromthe disconnected state to the armed state in response to actuation ofthe actuator 80, which operates as an arm switch. In response to thechange from the disconnected state to the armed state, the digitalcontrol circuit 212 generates a logic high signal on the output thatcauses the indicator 54 to become illuminated, and further stopsgenerating the logic high signal on the output that causes the indicator52 to be illuminated. In addition, the digital control circuit 212generates a signal identifying the change in state to the processor 48of the measurement module 14 via the connector block 88 a.

[0108] The digital control circuit 212 changes from the armed state tothe connected state in response to serial communication signals receivedfrom the processor 48 of the measurement module 14 through the connectorblock 88 a. The digital control circuit 212 also changes from the armedstate to the connected state in response to actuation of the actuator56, which operates as a connect switch. In response to the change fromthe armed state to the connected state, the digital control circuit 212generates a logic high signal on its CLOSE output, thereby causing theswitch contacts 25 a and 25 b to close. In addition, the digital controlcircuit 212 stops generating the logic high signal on the output thatcauses the indicator 52 to become illuminated. Finally, the digitalcontrol circuit 212 generates a signal identifying the change in stateto the processor 48 of the measurement module 14 via the connector block88 a.

[0109] The digital control circuit 212 may also monitor the mechanicalposition of the switch 25 in an independent manner. In particular, thedigital control circuit 212 may include a connection through the switchcontacts 25 a and/or 25 b which provide the digital control circuit 212with feedback as to the physical position of the switch contacts 25 aand 25 b. In this manner, the digital control circuit 212 may ensurethat the switch 25 is operating properly.

[0110]FIG. 8 shows a circuit block diagram of the measurement circuit 42and associated display 38 for use in the measurement module 14. Themeasurement circuit 42 includes a watt measurement integrated circuit(“IC”) 44, a controller or processor 48, a non-volatile memory 50 andone or more communication circuits 51. Plugs 40 a, 40 b, 40 c, 40 d, 40e, and 40 f are each connected to the watt measurement IC 44 throughvarious input circuits. In particular, the plugs 40 a and 40 b areconnected to the watt measurement IC 44 through a current input circuit312, the plugs 40 e and 40 f are connected to the watt measurement IC 44through a current input circuit 314, the plug 40 c is connected to thewatt measurement IC 44 through a voltage input circuit 316, and the plug40 d is connected to the watt measurement IC 44 through a voltage inputcircuit 318.

[0111] The current input circuit 312 is a device configured to obtain ascaled signal indicative of the line current waveform on the firstfeeder line. To this end, the current input circuit 312 is connectedacross a line resistor RLA1 that is series connected between the plug 40a and the plug 40 b. Plugs 40 a and 40 b, as discussed above and shownin FIGS. 2 and 8, are electrically connected to the first currenttransformer 16 a of the sensor module 12. Similarly, the current inputcircuit 314 is a device configured to obtain a scaled signal indicativeof the line current waveform on the second feeder line. To this end, thecurrent input circuit 314 is connected across a line resistor RLA2 thatis series connected between the plug 40 e and the plug 40 f. Plugs 40 eand 40 f, analogous to plugs 40 a and 40 b, are electrically connectedto the second current transformer 16 b of the sensor module 12. Theoutputs of the current input circuits 312 and 314 are provided to thewatt measurement IC 44.

[0112] The voltage input circuit 316 is a voltage divider network tappedoff of the connection to plug 40 c. Similarly, the input circuit 318 isa voltage divider network tapped off of the connection to the plug 40 d.The power supply 49 is a device that receives AC input line voltage andgenerates a DC supply voltage VDD therefrom. Such power supplies arewell known in the art. The power input to the power supply 49 ispreferably tapped off of the connection to the plug 40 d. The outputs ofthe voltage input circuits 316 and 318 are provided to the wattmeasurement IC 44.

[0113] The watt measurement IC 44 is a device that receives measurementsignals representative of voltage and current signals in an electricalsystem and generates energy consumption data therefrom. In the exemplaryembodiment described herein, the watt measurement IC 44 may suitably bethe conversion circuit 106 described in U.S. Pat. No. 6,112,158 or theconversion circuit 106 described in U.S. Pat. No. 6,112,159, both ofwhich are assigned to the assignee of the present invention andincorporated herein by reference.

[0114] Alternatively, the watt measurement IC 44 may be replaced by oneor more discrete circuits capable of carrying out the same function ofgenerating energy consumption information from the voltage and currentmeasurement signals. For example, the watt measurement IC 44 maysuitably be replaced by the first and second watt measurement ICs 44 and46 described in the U.S. Pat. No. 5,933,004, which is incorporatedherein by reference.

[0115] In any event, the watt measurement IC 44 is further operablyconnected to the microcontroller 48 through a bus structure 320. The busstructure 320 consists of one or more serial and or parallel busses thatallow for data communication between the microcontroller 48 and the wattmeasurement IC 44. In general, the watt measurement IC 44 providesenergy consumption data to the microcontroller 48 and themicrocontroller 48 provides control and calibration data to the wattmeasurement IC 44.

[0116] The microcontroller 48 is further operably connected to thememory 50, the communication circuit(s) 51, and the display circuit 38.The processor 48 is also operably coupled to communicate with the sensormodule 12, and more particularly, the digital control circuit 212 of theservice disconnect switch circuit (See FIGS. 6, 7) using serial datasignals. To effect such communication, the processor 48 is operablycoupled to communicate such signals through the connector block 88 c.

[0117] In the operation of the exemplary meter assembly 10 illustratedin FIGS. 2-8, energy consumption measurements are carried out in thefollowing manner. As discussed above, the present embodiment is intendedfor use with a wiring configuration commonly referred to in the industryas a single-phase three-wire configuration. A single phase three-wireconfiguration, as discussed above, typically includes a 240 volt linethat is bisected into two 120 volt lines for use by the load, referredto herein as the First line and the Second line. The present invention,however, is in no way limited to use in single-phase configurations. Theconcepts described herein may readily be implemented in meters used inother configurations, including polyphase configurations.

[0118] In operation, the plurality of jaws 22 provide the first bisectedpower line or First line signal across the blades 22 a and 24 a throughthe switch contact 25 a (see FIGS. 2, 3 and 6). Similarly, the pluralityof jaws 22 provide the second bisected power line or Second line signalacross the blades 22 b and 24 b through the switch contact 25 b (seeFIGS. 2, 3 and 6). Referring to FIG. 6, the First line current flowsfrom the blade 24 a through the switch contact 25 a to the blade 22 a.The current blade 22 a, which passes through the current transformer 16a, imposes a scaled version of the current, referred to herein as thefirst current measurement signal, on the first current transformer 16 a.The first current measurement signal is approximately equal to thecurrent flowing through the current blade 22 a scaled by a factor of N1,where N1 is the turns ratio of the current transformer 16 a. The firstcurrent measurement signal is provided to the sockets 30 a and 30 b. Thefirst contact blade 24 a is further provides the first voltagemeasurement signal (i.e. the actual voltage of the First line) to thesocket 30 c.

[0119] Similar to the First line current, the Second line current flowsfrom the blade 24 b through the switch contact 25 b to the current blade22 b. The current blade 22 b, which passes through the second currenttransformer 16 b, imposes a scaled version of the Second line currentonto the second current transformer 16 b, thereby causing the secondcurrent transformer 16 b to generate a second current measurementsignal. The second current measurement signal is approximately equal tothe Second line current scaled by a factor of N2, where N2 is the turnsratio of the second current transformer 16 b. The turn ratios N1 and N2of the current transformers 16 a and 16 b, respectively, are typicallysubstantially similar and preferably equal. However, manufacturingtolerances may result in slight differences in the turn ratios N1 andN2. In any event, the second current transformer 16 b provides thesecond current measurement signal to the sockets 30 e and 30 f. Theblade 24 b also provides the second voltage measurement signal (i.e. theactual voltage line signal) to the socket 30 d. The neutral blade 20provides a connection between the neutral power line and the socket 30g.

[0120] It is noted that potentially hazardous electrical signals resideon one or more of the sockets 30 a through 30 g. In particular, thesockets 30 c and 30 d provide a direct connection to the external orutility power line, and therefore are potentially extremely dangerous.Moreover, the sockets 30 a, 30 b, 30 e, and 30 f all include currentmeasurement signals that are potentially dangerous to humans, dependingsomewhat on the overall power consumption of the facility being meteredand the turn ratios N1 and N2. Accordingly, the relatively smallphysical size of the sockets 30 a through 30 g and their correspondingopenings greatly inhibits and preferably prevents human contact with thesocket connections.

[0121] Continuing with the general operation of the meter 10, thesockets 30 a and 30 b (FIG. 6) provide the first current measurementsignal to the plugs 40 a and 40 b, respectively, of the measurementmodule 14 (FIG. 8). Likewise, the sockets 30 e and 30 f (FIG. 6) providethe second current measurement signal to the plugs 40 e and 40 f,respectively, of the measurement module 14 (FIG. 8). The sockets 30 cand 30 d (FIG. 6), provide, respectively, the first and second voltagemeasurement signals to the plugs 40 c and 40 d (FIG. 8). The neutralsocket 30 g (FIG. 6) provides a neutral connection to the plug 40 g ofFIG. 8.

[0122] Referring again to FIG. 8, at least the basic metering functionsare provided by the measurement circuit 42 within the measurement module14. It will be noted, however, that the “basic metering functions” ofthe measurement circuit 42 may include far more than simple energymeasurement functions. For example, the basic metering functionsprovided by the measurement circuit 42 may include at least a part ofone or more advanced features typically associated with electricitymeters, such as time of use metering, load profiling, demand metering,as well as other features such as service type recognition, diagnostics,remote meter reading communications or the like.

[0123] In any event, the plugs 40 a and 40 b provide the first currentmeasurement signal to the watt measurement IC 44 through the currentinput circuit 312. The current input circuit 312 preferably converts thefirst current measurement signal to a voltage signal having a magnitudeand phase that is representative of the First line current. The socket40 c provides the first voltage measurement signal through the voltageinput circuit 316 to the watt measurement IC 44.

[0124] The plugs 40 e and 40 f similarly provide the second currentmeasurement signal to the watt measurement IC 44 through the currentinput circuit 314. The current input circuit 314 preferably converts thesecond current measurement signal to a voltage signal having a magnitudeand phase that is representative of the Second line current. The socket40 d provides the second voltage measurement signal through the voltageinput circuit 318 to the watt measurement IC 44. The socket 40 d furtherprovides the Second line voltage to the power supply 49. The powersupply 49 is further connected to the neutral plug 40 g and operates toprovide a supply voltage VDD to each of the functional block circuitswithin the measurement module 14.

[0125] The watt measurement IC 44 receives the voltage and currentmeasurement signals, and generates energy consumption data therefrom. Tothis end, the watt measurement IC 44 preferably samples, multiplies andaccumulates the measurement signals as is known in the art to generatewatt data, VA data, and/or VAR data. See, for example, U.S. Pat. No.6,112,158 or U.S. Pat. No. 6,112,159, as discussed above, for adescription of such operations.

[0126] The processor 48 then obtains watt data, VA data, and/or VAR dataand further processes the data to provide energy consumption informationin standard units in accordance with metering industry standards. Theenergy consumption information is communicated externally through thedisplay 38. Alternatively or additionally, the energy consumptioninformation may be communicated through the external communicationcircuit 51.

[0127] It is noted that in the exemplary embodiment described herein,the meter 10 is a type of meter commonly known in the industry as aself-contained meter. In a self-contained meter, the current coils ofthe meter, such as current blades 22 a and 22 b of the presentembodiment, carry the entire current load of the electrical system. As aresult, in a typical meter, if the meter is removed for repair orreplacement, the current coils are removed from the jaws of the meterbox, and power to the facility is interrupted. A distinct advantage ofthe present invention is that the measurement module 14 may be removedfor repair, replacement or upgrade without removing the current coils ofthe meter. As a result, the facility experiences no electrical serviceinterruption during the replacement.

[0128] Automated Operation of Service Disconnect Circuit

[0129] As discussed further above, it may be advantageous in somecircumstances to disconnect electrical service to the load connected tothe meter 10. For example, an electrical service provider may employremote disconnection of service to periodically disconnect the load fordelinquent payors. To this end, disconnection and arm signals may bereceived from the service provider's systems via the communicationcircuits 51. In such a case, the communication circuit(s) 51 may includea telephone modem, power line carrier communication circuit, and/or aradio communication circuit. In an alternative embodiment, it may beadvantageous to disconnect electrical service to a load in a prepaidenergy system. The disconnection would be employed when the prepaidenergy quantity was consumed. In such a case, the controller orprocessor 48 may automatically track consumption of prepaid amounts anddisconnect service when appropriate. In another alternative, theprocessor 48 may automatically cause electrical service to bedisconnected in response to energy rationing processes enabled withinthe processor 48.

[0130] Regardless of whether the processor 48 receives servicedisconnect circuit control signals from an external device or internallygenerates such control signals, the processor 48 provides correspondingdisconnect control signals to the digital control circuit 212 (see FIGS.6, 7, and 8) via the connectors 88 c and 88 a.

[0131] The digital control circuit 212 changes from the connected stateto the disconnected state upon receiving the disconnect control signalfrom the processor 48. During the state change, the digital controlcircuit 212 operates as discussed above in connection with FIG. 7 tocause the switch contacts 25 a and 25 b to open and to cause theindicator 52 to be illuminated. The illuminated indicator 52 providesthe customer (or other party) with a visual indication that service hasbeen disconnected via the service disconnect circuit of the meter 10.

[0132] At some subsequent time, the processor 48 will provide an armcommand signal to the digital control circuit 212. For example, theprocessor 48 may be programmed to allow reconnection of electricalservice after a brief interruption of service, upon full or partialpayment of amounts due, or upon subsequent prepurchase of additionalenergy. To allow reconnection of the electrical service to the load, theprocessor provides the arm control signal to the digital control circuit212 of the service disconnect circuit through the connectors 88 a and 88c.

[0133] As discussed above, the digital control circuit 212 changes fromthe disconnected state to the armed state upon receiving the arm commandsignal from the processor 48. The digital control circuit 212 operatesas discussed above in connection with FIG. 7 to illuminate the indicator54. The illuminated indicator 54 provides the customer (or other party)with a visual indication that service may now be re-connected becausethe service disconnect circuit of the meter 10 has been armed.

[0134] In accordance with one aspect of the present invention, thedigital control circuit 212 may only be changed from the armed state tothe connected state through actuation of the actuator 56. In thismanner, the dangers associated with remote or automatic reconnection ofelectrical service may be avoided. Moreover, the customer may avoidadditional unnecessarily costs of electricity consumption by having thechoice of whether to reconnect.

[0135] It is noted that in some prepaid energy situations, a smart cardor debit card may be inserted into a device that communicates with themeter locally. In such a case, the acceptance of prepayment could causethe digital control circuit 212 to change to the armed state andconnected state immediately.

[0136] However, in a normal situation which requires actuation of theconnect actuator 56, the digital control circuit 212 detects theactuation and changes from the armed state to the connected state. Thedigital control circuit 212 operates as discussed above in connectionwith FIG. 7 to close the switch contacts 25 a and 25 b. When the switchcontacts 25 a and 25 b are closed, then electrical power flows to theload connected to the blades 22 a and 22 b from the power linesconnected to the blades 24 a and 24 b.

[0137] Manual Operation of Service Disconnect Circuit

[0138] In some circumstances, it may be advantageous to allow atechnician the ability to disconnect electrical service to the loadconnected to the meter 10 using the service disconnect circuit. To thisend, the meter 10 includes disconnect and arm switches in the forms ofactuators 78 and 80. However, the actuators 78 and 80 are not accessibleto the customer because the measurement module 14 inhibits such accesswhen installed on the sensor module 12 (see FIGS. 1 and 2).

[0139] In order to access the actuators 78 and 80, the measurementmodule 14 must be removed from the sensor module 12. Such removaltypically causes a tamper event to occur. For example, removal of themeasurement module 14 may require compromise of a mechanical tamper sealthat can only be replaced by a qualified technician. Thus, access to theactuators 78 and 80 is effectively limited to qualified technicians.

[0140] In the event that a technician needs to perform an operation inwhich the technician needs to either disconnect or reconnect theelectrical service, the technician first removes the measurement module14 from the sensor module 12. The technician then actuates thedisconnect switch 78 if disconnection of service is desired or the armswitch 80 if reconnection of service is desired. In the case ofreconnection, the technician would further actuate the connect switch 56to cause power to be connected.

[0141] In further detail, when the technician actuates the disconnectswitch 78, the digital control circuit 212 detects the actuation andchanges from the connected state to the disconnected state in responsethereto. The digital control circuit 212 operates as discussed above inconnection with FIG. 7 to cause the switch contacts 25 a and 25 b toopen and to cause the indicator 52 to be illuminated. The indicator 52provides the technician with a visual indication that service has beendisconnected via the service disconnect circuit of the meter 10.

[0142] When the technician actuates the arm switch 80, the digitalcontrol circuit 212 detects the actuation and changes from thedisconnected state to the armed state in response thereto. The digitalcontrol circuit 212 operates as discussed above in connection with FIG.7 to illuminate the indicator 54. The indicator 54 provides thetechnician with a visual indication that service may now be re-connectedbecause the service disconnect circuit of the meter 10 has been armed.

[0143] When the technician (or other party) actuates the connectactuator 56, the digital control circuit 212 detects the actuation andchanges from the armed state to the connected state. The digital controlcircuit 212 operates as discussed above in connection with FIG. 7 toclose the switch contacts 25 a and 25 b. When the switch contacts 25 aand 25 b are closed, then electrical power flows to the load connectedto the blades 22 a and 22 b from the power lines connected to the blades24 a and 24 b.

[0144] The technician may cycle through multiple disconnection andreconnection operations, as desired, before replacing the measurementmodule 14.

[0145] Bypass Tamper Protection

[0146] As discussed above, one method of tampering that can defeat theoperation of the service disconnect circuit of the meter 10 consists ofimplementing a bypass connection in parallel to the service disconnectswitch contacts 25 a and/or 25 b. In accordance with one aspect of thepresent invention, the processor 48 of the measurement module 14cooperates with the voltage sense circuit 216 of the driver circuit 210to sense such bypass connections.

[0147] In general, the voltage sense circuit 216 is operable to providea logic signal that is representative of whether line voltage is presenton the feeder lines to the customer's load. Referring to FIGS. 6 and 7,when line voltage is present on the feeder lines, line voltage is alsopresent on the blades 22 a and 22 b. The voltage sense circuit inputs226 and 228 are electrically coupled to and thus obtain the line voltagefrom the blades 22 a and 22 b. The resistor network 230 of the voltagesense circuit 216 divides the line voltage and provides the divided linevoltage to the optical isolator bi-directional input 232. The dividedline voltage, which has a normal 50 or 60 Hz cycle, causes the one oftwo diodes of the bi-directional input 232 to be biased on through theentire AC cycle of the line voltage, except for the portions of the ACcycle directly adjacent to the zero crossings.

[0148] Because the bi-directional input 232 is biased on in such amanner, the receiver/output 236 causes VCC to be connected to the outputEXT1 through most of the AC cycle. Moreover, during the short time nearthe zero crossings of the AC cycle in which the bi-directional input 232is biased off, the capacitor 238 sustains the high logic level at EXT1.Thus, EXT1 remains at a constant high logic state while line voltage ispresent on the blades 22 a and 22 b.

[0149] When line voltage is not present on the feeder lines, then novoltage is present on the blades 22 a and 22 b, nor the voltage senseinput circuits 226 and 228. As a result, the bi-directional input 232 isbiased off and, as a result, the receiver/output 236 does not connectVCC to the output EXT1.

[0150] The processor 48 uses the EXT1 output and the state of theservice disconnect switch 25 to determine whether a tamper event hasoccurred. If the service disconnect switch 25 is open and EXT1 is at ahigh logic level, then the processor 48 records a tamper event. It willbe apparent that when the service disconnect switch 25 is closed, EXT1will be at a high logic level because line voltage is present at theload. However, no tamper event is recorded (at least in this tamperprotection operation) because line voltage should be present when theservice disconnect switch 25 is closed. The processor 48 obtains thestate of the service disconnect switch 25 through the communication ofthe state change by the digital control circuit 212 to the processor 48,discussed above.

[0151] It will be appreciated that the tamper detection arrangementdescribed above may readily be modified for use in non-modular meters.The tamper detection arrangement advantageously requires only a singleconnection to the processor 48, through the EXT1 connection (providedthrough connector assembly 88). The use of a single connection helpsconserve the limited resource of processor inputs in utility metercircuitry. Such an advantage is particularly useful in modular meters(wherein the processor is located in another module), but is also usefulin any processor-based meter. Moreover, the implementation of anisolation mechanism provides additional advantages of complete isolationbetween the power lines and the processor 48 useful in any meter design.

[0152] It will be appreciated that the above-described embodiments aremerely exemplary, and that those of ordinary skill in the art mayreadily devise their own implementations that incorporate the spirit ofthe present inventions and fall within the spirit and scope thereof.

We claim:
 1. An apparatus for determining tampering in an electricitymeter arrangement comprising: a service disconnect switch operable tocontrollably disconnect electrical power lines from a load, the loadincluding at least first and second feeder lines; a voltage sensecircuit coupled to sense voltage on the first and second feeder lines,the voltage sense circuit operable to generate a voltage detectionsignal based on a first voltage on the first feeder line and a secondvoltage on the second feeder line, the voltage detection signal having acharacteristic representative of whether line voltage from theelectrical power lines is present on the first and second feeder lines;and a processing circuit operably connected to the voltage sense circuitto receive the voltage detection signal, the processing circuit operableto selectively generate a tamper flag based on whether thecharacteristic of the voltage detection signal indicates the presence ofvoltage on the first and second feeder lines when the service disconnectswitch has disconnected the electrical power lines from the first andsecond feeder lines.
 2. The apparatus of claim 1 wherein the voltagesense circuit is further operable to generate a voltage detection signalhaving a first magnitude when line voltage is present on the first andsecond feeder lines and having a second magnitude when line voltage isnot present on the first and second feeder lines.
 3. The apparatus ofclaim 2 wherein the first magnitude and second magnitude are discretedigital signal levels.
 4. The apparatus of claim 1 wherein the voltagesense circuit includes a voltage divider operable to scale a voltagedifference between the first feeder line and the second feeder line. 5.The apparatus of claim 4 wherein: the voltage sense circuit furtherincludes an output switch; the voltage divider includes an outputcoupled to an output switch, the output switch biased on the voltagedivider provides a voltage exceeding a predetermined level, the outputswitch operably coupled to provide the voltage detection signal to theprocessing device, the voltage detection signal varying based on whetherthe output switch is biased on.
 6. The apparatus of claim 5 wherein theoutput switch is coupled to the voltage divider output through anoptical isolator.
 7. The apparatus of claim 5 wherein the processingcircuit is further operable to obtain digital values from a metermeasurement circuit and generate metering information therefrom.
 8. Theapparatus of claim 1 wherein the voltage sense circuit includes anoutput switch, the output switch biased on when line voltage is presenton the first and second feeder lines, the output switch operably coupledto provide the voltage detection signal to the processing device, thevoltage detection signal varying based on whether the output switch isbiased on.
 9. The apparatus of claim 1 wherein the voltage sense circuitfurther includes an isolation mechanism, said isolation mechanismisolating the processing circuit from the first and second feeder lines.10. The apparatus of claim 1 wherein the voltage sense circuit includesan optical isolation circuit.
 11. An apparatus for determining tamperingin an electricity meter arrangement comprising: a housing containing ametering circuit; a service disconnect switch disposed within thehousing, the service disconnect switch operable to controllablydisconnect electrical power lines from a load, the load including atleast first and second feeder lines; a voltage sense circuit coupled tosense voltage on at least one feeder line, the voltage sense circuitincluding an isolation mechanism interposed between the at least onefeeder line and an output, the voltage sense circuit operable togenerate a voltage detection signal having a characteristicrepresentative of whether line voltage from the electrical power linesis present on the at least one feeder line, the voltage sense circuitoperable to provide the voltage detection signal to the output; and aprocessing circuit operably connected to the output to receive thevoltage detection signal, the processing circuit operable to selectivelygenerate a tamper flag based on whether the characteristic of thevoltage detection signal indicates the presence of voltage on the atleast one feeder line when the service disconnect switch hasdisconnected the electrical power lines from the first and second feederlines.
 12. The apparatus of claim 11 wherein the voltage sense circuitis further operable to generate a voltage detection signal having afirst magnitude when line voltage is present on the at least one feederline and having a second magnitude when line voltage is not present onat least one feeder line.
 13. The apparatus of claim 12 wherein thefirst magnitude and second magnitude are discrete digital signal levels.14. The apparatus of claim 1 wherein the voltage sense circuit includesan output switch, the output switch biased on when line voltage ispresent on the at least one feeder line, the output switch operablycoupled to provide the voltage detection signal to the output, thevoltage detection signal varying based on whether the output switch isbiased on.
 15. The apparatus of claim 14 wherein the output switch is anoptical receiver, the optical receiver including a portion of theisolation mechanism.
 16. The apparatus of claim 11 wherein the isolationmechanism includes an optical isolation circuit.
 17. A methodcomprising: a) disconnecting, using a service disconnect switch, atleast one feeder line of a load from at least one electrical power line,the service disconnect switch disposed within an electricity meterhousing; b) employing a voltage sense circuit that is operably connectedto the at least one power line to generate a voltage detection signalhaving a characteristic representative of whether line voltage from theelectrical power lines is present on the at least one feeder line; c)providing the voltage detection signal to an output that is electricallyisolated from the at least one feeder line; d) employing a processingcircuit to receive the voltage detection signal and generate a tamperflag if the characteristic of the voltage detection signal indicates thepresence of line voltage on the at least one feeder line.
 18. The methodof claim 17 wherein step b) further includes employing the voltage sensecircuit to generate the voltage detection signal such that the voltagedetection signal has a first magnitude when line voltage is present onthe at least one feeder lines and the voltage detection signal has asecond magnitude when line voltage is absent from the at least onefeeder line.
 19. The method of claim 18 wherein step b) further includesemploying the voltage sense circuit to generate the voltage detectionsignal such that the first magnitude and the second magnitude arediscrete digital voltage levels.
 20. The method of claim 17 furtherincluding: e) employing the processing circuit to perform a meteringcalculation.